Defining one's terms

Last night, my "front-porch salon" convened to begin our discussion of Peter Kreeft's A Shorter Summa. (See related posts here and here.) It was a marvelous time, full of lively conversation, probing questions, and thoughtful reflections. (Thanks, gentlemen.) We commenced by reading from Kreeft's introduction:

The reader will be constantly confused if he does not first have in his mind a very clear idea of the differences between terms (which are either clear or unclear), propositions (which are either true or false), and arguments (which are either logically valid or invalid).

I want to dwell for a minute on the importance of terms. Essential to any conversation is clarity about the meaning of key words that will be spoken and heard. For example, if you think "pear" when I say "banana," we're not going to have a very productive conversation about fruit. The more important the term to the conversation, the more important it is to define it.

Definitions do place limits around a conversation, but limits can be liberating in the sense that they direct parties toward its object. For instance, if you and I are discussing where to buy a bottle of wine, the conversation will be shorter -- more limited -- if we both speak English. If you speak, say, Swahili, we may have a longer conversation, but we stand less of a chance of achieving our objective -- finding a bottle of wine -- since I'm probably not going to understand much of what you're saying.

Earlier this month, the Vatican attempted to define a term that has been bandied about since Vatican II: subsistence. They did so by restating what the Church has always taught about herself (tip, Russell Shaw):

'Subsistence' means...perduring, historical continuity and the permanence of all the elements instituted by Christ in the Catholic Church, in which the Church of Christ is concretely found on this earth.

You'd think this would be recognized as a positive development, for all the reasons, e.g., clarity, efficacy, comprehension, listed above. (Several Orthodox bishops thought so.) But then you probably haven't spent much time at Xavier University's Bellarmine Chapel, where, according to Richard Bollman, S.J., defining one's terms causes more, not less, misunderstanding:

So now in 2007, a five page reflection on the earlier document appears, to answer some of the questions that still come forward. Attempts to shut down inquiry always fail, it seems to me, and simply create more misunderstanding about what a teaching actually means, and what it doesn’t mean. Certainly nothing new has been added to the discussion through these five pages, though it all offers a chance for some catchy reporting in the press.